Answer the following questions
1.What is the basis of classification of elements in modern periodic table?
2.Write modern periodic law?
3.What are groups and periods in a periodic table?
4.How many groups and periods are there in a periodic table?
5.Write the names of groups (element families ) of periodic table?
6.What happens to the size of the atom from top to bottom in a group? Why?
7.What happens to the size of the atom from left to right in a period? Why?
8.What is ionization energy?
9.What are the factors that influences ionization energy of elements?
10.What is the change in ionisation energy down the group and along a period?
Answers
Answer:
(1) The modern classification is based on the atomic number of the element. The periodic law state that the physical and chemical properties of the element are the periodic function of their atomic number. Therefore the variation in the properties of element is related with its electronic configuration.
(2) The modern Periodic law can be stated as: “The physical and chemical properties of the elements are periodic functions of their atomic numbers”. The atomic number is equal to the number of electrons or protons in a neutral atom.
(3) The columns of the periodic table are called groups. Members of the same group in the table have the same number of electrons in the outermost shells of their atoms and form bonds of the same type. The horizontal rows are called periods.
(4) There are eighteen vertical columns known as groups in the modern periodic table which are arranged from left to right and seven horizontal rows which are known as periods.
(5)
•Group 1: alkali metals, or lithium family.
•Group 2: alkaline earth metals, or beryllium family.
•Group 3: the scandium family.
•Group 4: the titanium family.
•Group 5: the vanadium family.
•Group 6: the chromium family.
(6) On going down in a group of the periodic table, the atomic size increases. When we move from top to bottom in a group, a new shell of electrons is added to the atoms at every step due to which the size of atom increases.
(7) Atomic size gradually decreases from left to right across a period of elements. This is because, within a period or family of elements, all electrons are added to the same shell. The valence electrons are held closer towards the nucleus of the atom. As a result, the atomic radius decreases.
(8) ionization energy or ionisation energy is the minimum amount of energy required to remove the most loosely bound electron of an isolated neutral gaseous atom or molecule.
(9) 3 Factors Affecting Ionisation Energy
•Size of the positive nuclear charge.
As the nuclear charge increases, its attraction for the outermost electron increases and more energy is required to remove an electron.
•Size of atom (distance of outermost electron from the nucleus).
•Screening (shielding) effect of inner shell electrons.
(10) Ionization energy increases from left to right in a period and decreases from top to bottom in a group.
Explanation: